Steam-releasing flat pouch

ABSTRACT

The steam-releasing flat pouch comprises a seal part, a steam-releasing seal part, and a steam discharge part. The seal part seals stacked sheets. The steam-releasing seal part is located in the inner parts of the sheet inside the seal part, and is configured to join parts of the sheet so that they are not continuous with the seal part. The steam discharge part is formed in the steam-releasing seal part and configured not to allow communication with the outside when the steam-releasing seal part is not peeled, and to allow communication with the outside when the steam-releasing seal part is peeled. The steam-releasing seal part includes an anterior peeling part including a part that peels apart first as the pressure increases, and a posterior peeling part including a part that peels apart last. The width of the posterior peeling part is smaller than the width of the anterior peeling part.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

This application is a continuation application filed under 35 U.S.C. §111(a) claiming the benefit under 35 U.S.C. §§ 120 and 365(c) ofInternational Patent Application No. PCT/JP2018/029745, filed on Aug. 8,2018, which is based upon and claims the benefit of priority to JapanesePatent Application No. 2017-157175, filed on Aug. 16, 2017; thedisclosures of which are all incorporated herein by reference in theirentireties.

TECHNICAL FIELD

The present invention relates to a steam-releasing flat pouch.

BACKGROUND

A steam-releasing flat pouch which discharges water vapor, generatedfrom its contents by heating the contents, to the outside is known. PTL1 discloses an example of a conventional steam-releasing pouch. As shownin FIG. 11, the steam-releasing flat pouch (100) of PTL 1 comprises alaminate (150) that forms an storage space (110) in which the contentsare stored, and a heat-welded part (120) where the laminate (150) isjoined so that the storage space (110) is closed. The heat-welded part(120) includes an outer peripheral part (121) corresponding to the outershape of the steam-releasing flat pouch (100), and a protruded part(130) formed so as to protrude from the outer peripheral part (121)toward the storage space (110). At a portion surrounded by the outerperipheral part (121) and the protruded part (130), a notch (140) isformed which communicates the outside of the steam-releasing flat pouch(100) in a state where the storage space (110) is closed by theheat-welded part (120). In a state where the protruded part (130) isjoined with the laminate (150), since the space between the storagespace (110) and the notch (140) is closed by the protruded part (130),the contents in the storage space (110) do not move to the notch (140).

When the steam-releasing flat pouch (100) is heated by a heating meanssuch as a microwave oven, the pressure in the storage space (110) isincreased by the water vapor generated from the contents, and a force isexerted on the protruded part (130) that causes the protruded part(130), more specifically, the upper laminate (151) and the lowerlaminate (152) constituting the protruded part (130) to peel apart. Whenthe pressure in the storage space (110) rises to a certain level, a partof the protruded part (130) peels apart as shown in FIG. 12, and thepeeling of the protruded part (130) proceeds towards the outerperipheral part (121) of the heat-welded part (120). As shown in FIG.13, when the peeling of the protruded part (130) reaches the notch(140), the storage space (110) and the outside of the steam-releasingflat pouch (100) are communicated via the notch (140), and the watervapor in the storage space (110) is discharged to the outside throughthe notch (140).

-   [Citation List] [Patent Literature] [PTL 1]JP H11208739 A

SUMMARY OF THE INVENTION Technical Problem

According to the above-described steam releasing flat pouch (100), inthe state where the storage space (110) and the outside of thesteam-releasing flat pouch (100) communicate with each other through thenotch (140), the upper laminate (151) and the lower laminate (152) arecommunicated with each other at the heat-welded part (120) which is apart of the portion of the laminate (150) where the notch (140) isformed. Thus, when the distance between the notch (140) and the contentsis short and water vapor is being discharged from the notch (140), thecontents may leak from the notch (140) together with the water vapor.

Solution to Problem

(1) A steam-releasing flat pouch according to the present inventioncomprises, a seal part configured to seal stacked sheets so as to forman storage space for storing contents, a steam-releasing seal partjoining parts of the sheets respectively located in inner parts of thesheets so that the joined parts are not continuous with the seal part,each inner part being a part of the corresponding sheet inside the sealpart, and a steam discharge part formed in the steam-releasing seal partand configured not to allow the storage space to communicate with theoutside when the steam-releasing seal part is not peeled apart, and toallow the storage space to communicate with the outside when thesteam-releasing seal part is peeled apart, wherein the steam-releasingseal part includes an anterior peeling part including a part that peelsapart first in the steam-releasing seal part as a pressure in thestorage space increases, and a posterior peeling part including a partthat peels apart last in the steam-releasing seal part, and, a width ofthe posterior peeling part in a direction different from a direction inwhich peeling of the steam-releasing seal part proceeds is smaller thana width of the anterior peeling part in the direction different from thedirection in which the peeling proceeds.

When the steam-releasing flat pouch whose storage space is closed by theseal part is heated by the heating means, in an example, the pouch isset such that one of the stacked sheets is positioned below, and theother of the stacked sheets provided with the steam discharge part ispositioned above. In this state, when the steam-releasing flat pouch isheated, the pressure in the storage space is increased by the steamgenerated from the contents, and a force for causing the steam-releasingseal part to peel apart is applied to the steam-releasing seal part.Once the pressure in the storage space rises to a certain level, peelingof the steam-releasing seal part starts from the anterior peeling partand the peeling of the steam-releasing seal part proceeds toward theposterior peeling part. When the peeling of the steam-releasing sealpart reaches the steam discharge part, the steam discharge part allowsthe storage space to communicate with the outside. Therefore, the steamin the storage space is discharged to the outside through the steamdischarge part. Thus, the increase in pressure in the storage space issuppressed, and the force for causing the steam-releasing seal part topeel apart is reduced. However, since the width of the posterior peelingpart is smaller than the width of the anterior peeling part, a situationwhere the peeling of the steam-releasing seal part stops before the endof the posterior peeling part is unlikely to occur. When the peeling ofthe steam-releasing seal part reaches the end of the posterior peelingpart, the portion of the sheet on top that has been joined by thesteam-releasing seal part moves upward so as to be separated from thesheet below and the contents. In the above-described steam-releasingflat pouch, the steam-releasing seal part is formed in the inner part,and the steam discharge part is formed in the steam-releasing seal part.Thus, when the sheet on top moves upward, the steam discharge part alsomoves upward so as to be separated from the sheet below and thecontents. Thus, the contents are unlikely to leak when the steam isdischarged.

(2) According to a preferable example, in the steam-releasing flat pouchaccording to (1), the posterior peeling part is formed so that the widththereof becomes narrower toward the direction in which the peelingproceeds.

Thus, when the force which causes the steam-releasing seal part to peelapart is applied to the steam-releasing seal part, local stressconcentration is unlikely to occur in the steam-releasing seal part.

(3) According to a preferable example, in the steam-releasing flat pouchaccording to (1) or (2), the steam discharge part includes a cut or anaperture penetrating one of the stacked sheets, and is formed so as toextend in the direction in which the peeling proceeds.

In a state where the peeling of the steam-releasing seal part has notreached the aperture or cut of the steam discharge part, the aperture orcut does not allow the storage space to communicate with the outside. Ina state where the peeling of the steam-releasing seal part has reachedthe aperture or cut, the aperture or cut allows the storage space tocommunicate with the outside, and the area (hereinafter referred to ascommunication area) of the aperture or cut that directly communicatesbetween the storage space with the outside increases as the peelingprogresses. Since the above-described steam-releasing flat pouch isformed so that the aperture or cut extends in the peeling progressdirection, the communication area gradually increases as the peelingproceeds. Thus, the flow rate of the steam discharged outside from thestorage space does not increase rapidly, and it helps the peeling of thesteam-releasing seal part to reach the end of the posterior peelingpart.

(4) According to a preferable example, in the steam-releasing flat pouchaccording to any one of (1) to (3), the pouch further comprises a guidepart constituting a guide for separating the sheets and a part of theseal part in order to open the storage space closed by the seal part,and the steam-releasing seal part is provided in parts of the sheetsthat are separated by the guide part.

Thus, when the portions of the sheets to be separated (hereinafterreferred to as separable part) by the guide part are separated, thesteam discharge part does not remain in the portions of the sheets thatstore the contents, and the contents do not leak from the steamdischarge part when contents are extracted from the storage space.

(5) According to a preferable example, in the steam-releasing flat pouchaccording to any one of (1) to (4), a dimension of the steam dischargepart in the direction in which the peeling proceeds is 12.5% or largerof a dimension of the steam-releasing seal part in the direction inwhich the peeling proceeds.

If the dimension of the steam discharge part is within the above range,steam is appropriately discharged from the steam discharge part when thestorage space communicates with the outside through the steam dischargepart.

(6) In a preferable example, in the steam-releasing flat pouch accordingto any one of (1) to (5), a dimension of the steam discharge part in thedirection in which the peeling proceeds is 62.5% or smaller of adimension of the steam-releasing seal part in the direction in which thepeeling proceeds.

If the dimension of the steam discharge part is within the above range,foreign substance is unlikely to enter the steam discharge part.

(7) According to a preferable example, in the steam-releasing flat pouchaccording to any one of (1) to (6), the pouch further comprises thecontents contained in the storage space.

Advantageous Effects of Invention

According to the steam-releasing flat pouch of the present invention,the contents are unlikely to leak when steam is discharged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front view of a steam-releasing flat pouch according to anembodiment of the present invention.

FIG. 2 is an enlarged view of the steam-releasing seal part in FIG. 1and its surroundings.

FIG. 3 is a front view of a steam-releasing flat pouch before an openingthereof is closed.

FIG. 4 is a front view of a steam-releasing flat pouch in a state wherea part of the steam-releasing seal part in FIG. 1 is peeled.

FIG. 5 is a front view of a steam-releasing flat pouch in a state wherethe steam-releasing seal part in FIG. 4 is completely peeled.

FIG. 6 is a cross-sectional view taken along the line D6-D6 of FIG. 5.

FIG. 7 is a table showing test conditions of Comparative Examples andExamples regarding tests.

FIG. 8 is a table showing test results of Comparative Examples andExamples.

FIG. 9 is an enlarged view of the steam-releasing seal part and itssurroundings according to a modification.

FIG. 10 is an enlarged view of the steam-releasing seal part and itssurroundings according to a modification.

FIG. 11 is a front view of a conventional steam-releasing flat pouch.

FIG. 12 is a cross-sectional view taken along the line D12-D12 of FIG.11.

FIG. 13 is a cross-sectional view showing a state where the protrudedpart of FIG. 12 is peeled.

DETAILED DESCRIPTION

With reference to the accompanying Figures, a description will now begiven of representative embodiments according to the present invention.The present invention is not limited to the following representativeembodiments, and appropriate modifications can be made without departingfrom the spirit of the present invention. The representative embodimentsdescribed below are merely examples of the present invention, and thedesign thereof could be appropriately changed by one skilled in the art.Here, the drawings are schematic, and the relationship between thicknessand plane size, the ratio of the thickness of each layer, etc., may bedifferent from actual ones. The embodiments described below are merelyexamples of the configurations for embodying the technical idea of thepresent invention, and the technical idea of the present inventionshould not limit the materials, shapes, structures, and the like of thecomponents to those described below. The technical idea of the presentinvention can be modified in various ways within the technical scopespecified by the claims.

The same constituent elements are denoted by the same reference numeralsunless there is a reason for the sake of convenience, and redundantdescription is omitted. In the drawings referred to in the followingdescription, for clarity, characteristic parts are enlarged, and thusthe components are not shown to scale. It is, however, clear that one ormore embodiments can be implemented without such details. In addition,known structures and devices may be schematically represented forsimplicity.

Embodiments

FIG. 1 shows an example of a steam-releasing flat pouch 10 that canstore contents C suitable for heating and can discharge the water vaporgenerated at the contents C. The contents C generate water vapor whenthey are heated. An example of the contents C is food. An example isfood cooked by heating. For example, the food may be ingredients of beefbowl, a hamburger steak, or stew. The steam-releasing flat pouch 10 isconfigured to store the contents C for a long period maintaining theirquality.

The steam-releasing flat pouch 10 includes a sheet 20, a seal part 30,an opening 40 (see FIG. 3), a guide part 50, a steam-releasing seal part60, and a steam discharging part 70. The dots in FIG. 1 and otherdrawings represent the seal part 30 and the steam-releasing seal part60. The sheet 20 include a first sheet 21 and a second sheet 22. Thefirst sheet 21 and the second sheet 22 are facing each other so as toform a storage space 10C between the sheets 21 and 22 for storing thecontents C. The configuration of the sheet 20 can be optionallyselected. In a first example, the sheets 21 and 22 are two sheets formedindividually. In a second example, the facing sheets 21 and 22 areformed by folding a single sheet.

The sheet 20 (the sheets 21 and 22) has a layered structure in which aplurality of layers are laminated. The layered structure of the sheet 20(the sheets 21 and 22) can be optionally selected. In the first example,the sheets 21 and 22 have the same layered structure. In the secondexample, the first and second sheets 21 and 22 have different layeredstructures. FIG. 1 shows a steam-releasing flat pouch 10 constituted bya sheet 20 having the layer structure of the first example.

Each of the sheets 21 and 22 includes an outermost layer, anintermediate layer, and an innermost layer. An example of a method formanufacturing the sheets 21 and 22 is dry lamination. The outermostlayer mainly excels in gloss, printing suitability, and retortresistance. Retort resistance means resistance to retort processing. Anexample of the material forming the outermost layer is a transparentmaterial. An example of a transparent material is polyethyleneterephthalate. The intermediate layer mainly excels in retortresistance, moisture resistance, and gas barrier properties. Theintermediate layer includes a printed layer, a first adhesive layer, anoriented nylon layer, and a second adhesive layer. The printed layer isplaced on the inner side of the outermost layer. In one example, theprinted layer is formed with patterns, texts such as item description,and the like printed on the outer surface thereof. The first adhesivelayer is placed on the inner side of the printed layer. The orientednylon layer is formed on the inner side of the first adhesive layer. Thesecond adhesive layer is formed on the inner side of the oriented nylonlayer. An example of the material forming each adhesive layer is a drylaminate adhesive. The innermost layer excels in retort resistance, heatsealability, and impact resistance. The innermost layer is placed on theinner side of the second adhesive layer. An example of the materialconfiguring the innermost layer is non-oriented polypropylene.

The seal part 30 joins the sheets 21 and 22 so that the sheets 21 and 22are not separated. In one example, the seal part 30 joins the innermostlayer of the first sheet 21 and the innermost layer of the second sheet22. An example of the method for forming the seal part 30 is heatsealing. The outer shape of the steam-releasing flat pouch 10 in frontview can be optionally selected. In the example shown in FIG. 1, theouter shape of the steam-releasing flat pouch 10 is a rectangle. Thesheet 20 can be divided into a portion surrounded by the seal part 30(hereinafter referred to as inner part 23) and the seal part 30. Thestorage space 10C is a space surrounded by the inner part 23 of thefirst sheet 21 and the inner part 23 of the second sheet 22, and isclosed by the seal part 30 so as not to communicate with the outside ofthe steam-releasing flat pouch 10.

The seal part 30 joins the first sheet 21 and the second sheet 22 sothat the storage space 10C is closed. The seal part 30 is divided intofirst to fourth seal parts 31 to 34. The first seal part 31 is formedalong the first side 20A of the sheet 20. The second seal part 32 isformed along the second side 20B of the sheet 20. The third seal part 33is formed along the third side 20C of the sheet 20. The fourth seal part34 is formed along the fourth side 20D of the sheet 20. The first sealpart 31, the third seal part 33, and the fourth seal part 34 are formedahead of the second seal part 32 in order to store the contents in thestorage space 10C. In a state where the first seal part 31, the thirdseal part 33, and the fourth seal part 34 are formed but the second sealpart 32 is not formed, an opening 40 for putting the contents into thestorage space 10C (see FIG. 3) is formed in the steam-releasing flatpouch 10. The second seal part 32 is formed after the contents are putinto the storage space 10C, and then the opening 40 is closed by thesecond seal part 32. In the following, the direction along the firstside 20A and the second side 20B in the front view of thesteam-releasing flat pouch 10 is referred to as a first direction, andthe direction along the third side 20C and the fourth side 20D isreferred to as a second direction.

An inner edge 31A which is an edge of the first seal part 31 on theinner part 23 side, an inner edge 32A which is an edge of the secondseal part 32 on the inner part 23 side, an inner edge 33A which is anedge of the third seal part 33 on the inner part 23 side, and an inneredge 34A which is an edge of the fourth seal part 34 on the inner part23 side define the outer shape of the inner part 23. An outer edge 31Bwhich is the edge of the first seal part 31 opposite to the inner edge31A, an outer edge 32B which is the edge of the second seal part 32opposite to the inner edge 32A, an outer edge 33B which is the edge ofthe third seal part 33 opposite to the inner edge 33A, and an outer edge34B which is the edge of the fourth seal part 34 opposite to the inneredge 34A define the outer shape of the steam-releasing flat pouch 10.

The width of each of the seal parts 31 to 34 can be optionally selected.The width of each seal part 31 to 34 is the distance between the inneredges 31A to 34A and the outer edges 31B to 34B along a normal line ofthe center line in each seal part 31 to 34. The center line of each sealpart 31 to 34 is an imaginary line segment passing between the inneredges 31A to 34A and the outer edges 31B to 34B. When the width of eachof the seal parts 31 to 34 vary for each portion, for example, themaximum width or the average widths of the plurality of portions in eachof the seal parts 31 to 34 represents the width of respective seal part.

Preferably, the dimension in the first direction and the dimension inthe second direction of the steam-releasing flat pouch 10 aredetermined, for example, from the relationship between the amount ofcontents C to be stored and the ease of carrying the steam-releasingflat pouch 10. The dimension in the first direction of thesteam-releasing flat pouch 10 is the length of a line segment orthogonalto the second direction between the outer edge 33B of the third sealpart 33 and the outer edge 34B of the fourth seal part 34. When thedimension of the steam-releasing flat pouch 10 in the first directiondiffer for each portion, for example, the maximum dimension or theaverage dimension of the plurality of portions represents the dimensionof the steam-releasing flat pouch 10 in the first direction. In oneexample, the dimension of the steam-releasing flat pouch 10 in the firstdirection is 130 mm. The dimension in the second direction of thesteam-releasing flat pouch 10 is the length of a line segment orthogonalto the first direction between the outer edge 31B of the first seal part31 and the outer edge 32B of the second seal part 32. When the dimensionof the steam-releasing flat pouch 10 in the second direction differs foreach portion, for example, the maximum dimension or the averagedimension of the plurality of portions represents the dimension of thesteam-releasing flat pouch 10 in the second direction. In one example,the dimension of the steam-releasing flat pouch 10 in the seconddirection is 135 mm.

The opening 40 (see FIG. 3) is formed between a lower part 21A of thefirst sheet 21 and a lower part 22A of the second sheet 22 so that thecontents C can be filled into the storage space 10C. In thesteam-releasing flat pouch 10 shown in FIG. 1, the opening 40 is closedby the second seal part 32. The steam-releasing flat pouch 10 of theopening 40 being closed (hereinafter referred to as closedsteam-releasing flat pouch 10) includes a pouch body 10A and a separablepart 10B. The pouch body 10A and the separable part 10B are segmented bya perforated line 51 constituting a guide part 50. The pouch body 10A isa part for storing the contents C. The separable part 10B is a part ofeach of the sheets 21 and 22 including the first seal part 31, and it isa part that the user separates from the pouch body 10A in order toextract the contents C from the storage space 10C.

The guide part 50 is formed between the pouch body 10A and the separablepart 10B so that each of the sheets 21 and 22 is easily cut when theseparable part 10B is separated from the pouch body 10A. The guide part50 includes a perforated line 51 and a notch 52. The perforated line 51is a group of perforations formed in the seal parts 33 and 34 and theinner part 23 of the sheets 21 and 22, and is formed as a straight line.The notch 52 is formed in at least one of the third seal part 33 or thefourth seal part 34 such that the tip of the notch 52 is located on animaginary line obtained by extending the perforated line 51. FIG. 1shows an example where the notch 52 is formed in both of the third sealpart 33 and the fourth seal part 34.

The steam-releasing flat pouch 10 is heated by heating means (heatingdevice) in order to heat the contents C. An example of the heating meansis a microwave oven. Steam is generated from the contents C as thesteam-releasing flat pouch 10 is heated. Because the storage space 10Cof the closed steam-releasing flat pouch 10 is closed by the seal part30, the pressure in the storage space 10C increases as steam isgenerated.

In the inner part 23, a steam-releasing seal part 60 is a part where theinnermost layer of the first sheet 21 and the innermost layer of thesecond sheet 22 are joined, and it is configured such that, as thepressure in the storage space 10C increases, peeling apart of theinnermost layer of the first sheet 21 and the innermost layer of thesecond sheet 22 occur. In the following, the phrase “the steam-releasingseal part 60 peels apart” means that the innermost layer of the firstsheet 21 and the innermost layer of the second sheet 22 bothconstituting the steam-releasing seal part 60 peel apart from eachother. In a preferred example, the steam-releasing seal part 60 isconfigured to be peeled apart when the pressure in the storage space 10Crises to a predetermined pressure. A steam discharge part 70 allows thestorage space 10C to communicate with the outside of the steam-releasingflat pouch 10 when the steam-releasing seal part 60 peels apart so as todischarge steam generated at the contents C to the outside of thesteam-releasing flat pouch 10. By discharging the steam from the steamdischarge part 70, the increase in the pressure of the storage space 10Cis suppressed, and rupture of the steam-releasing flat pouch 10 isavoided. The steam discharge part 70 is provided in the inside of theouter shape of the steam-releasing seal part 60.

The steam-releasing seal part 60 is provided so as not to be continuouswith the seal part 30. Since the steam-releasing seal part 60 isseparated from the seal part 30, the steam discharge part 70 is formedat a distance from the seal part 30 in the sheet 20. There may be one ormore steam-releasing seal parts 60 provided in the inner part 23. Thesteam-releasing seal part 60 is provided at any suitable location in theinner part 23. In a preferred example, the steam-releasing seal part 60is provided at a place where high stress concentration occurs when thepressure in the storage space 10C increases. In a first example, thesteam-releasing seal part 60 is provided in the separable part 10B at aposition facing the center of the first seal part 31 in the longitudinaldirection. In the first example, when the separable part 10B isseparated from the pouch body 10A, the steam-releasing seal part 60 doesnot remain in the pouch body 10A, and thus the contents C would not leakfrom the steam discharge part 70 when the contents C are removed fromthe storage space 10C. In a second example, the steam-releasing sealpart 60 is provided in the pouch body 10A.

FIG. 2 is an enlarged view of the steam-releasing seal part 60 and itssurroundings. The outer shape of the steam-releasing seal part 60 maytake various shapes. Examples include a triangle, a shape similar to atriangle, a trapezoid, a shape similar to a trapezoid, and a convexshape. In the example shown in the figure, the outer shape of thesteam-releasing seal part 60 is an isosceles triangle. The sidesconstituting the isosceles triangle are a first side 60A and a secondside 60B, both having equal sides, and a third side 60C which is thebottom side. In the first direction, the seal width XA of thesteam-releasing seal part 60 is the distance between the first side 60Aand the second side 60B.

When the pressure in the storage space 10C increases due to heating ofthe steam-releasing flat pouch 10, the steam-releasing seal part 60peels apart, and the peeling of the steam-releasing seal part 60proceeds as the pressure increases. When the peeling of thesteam-releasing seal part 60 reaches the steam discharge part 70, thestorage space 10C and the outside of the steam-releasing flat pouch 10communicate with each other via the steam discharge part 70. The area ofthe steam discharge part 70 directly communicating with the storagespace 10C, that is, the communication area of the steam discharge part70 becomes greater as the peeling of the steam-releasing seal part 60proceeds. Assuming that the pressure in the storage space 10C isconstant, the flow rate of steam discharged to the outside of thesteam-releasing flat pouch 10 through the steam discharge part 70increases as the communication area of the steam discharge part 70increases. The communication area is zero in a state where thesteam-releasing seal part 60 does not peel apart, and in a state wherethe peeling of the steam-releasing seal part 60 has not reached thesteam discharge part 70. When the steam-releasing seal part 60surrounding the steam discharge part 70 entirely peels apart, thecommunication area becomes the largest.

The steam-releasing seal part 60 includes an anterior peeling part 61including a part that peels apart first in the steam-releasing seal part60 and a posterior peeling part 62 including a part that peels apartlast in the steam-releasing seal part 60. In the example shown in thefigure, the portion of the steam-releasing seal part 60 that peels apartfirst is a part or all of the third side 60C. The portion of thesteam-releasing seal part 60 that peels apart last is the apex 60D. Theseal width XA of the posterior peeling part 62 in a direction differentfrom the direction in which the peeling of the steam-releasing seal part60 proceeds is smaller than the seal width XA of the anterior peelingpart 61 in a direction different from the direction in which the peelingof the steam-releasing seal part 60 proceeds. An example of the“different direction” is a crossing direction, and a preferred exampleis the direction orthogonal to the other direction.

The anterior peeling part 61 includes, for example, the following partsof the steam-releasing seal part 60. In a first example, the anteriorpeeling part 61 includes the portion of the steam-releasing seal part 60extending from the third side 60C to the steam discharge part 70. In thefirst example, the anterior peeling part 61 does not include the end ofthe steam discharge part 70 on the side of the storage space 10C(hereinafter referred to as inner end of the steam discharge part 70).When the range of the anterior peeling part 61 is defined as in thefirst example, the steam discharge part 70 does not communicate with thestorage space 10C until peeling of the steam-releasing seal part 60reaches the posterior peeling part 62. Because the communication area isrelatively small in a state immediately after the peeling of thesteam-releasing seal part 60 has reached the steam discharge part 70,the force acting to peel the steam-releasing seal part 60 is high.Therefore, the peeling of the posterior peeling part 62 proceedssmoothly following the peeling of the anterior peeling part 61. In asecond example, the anterior peeling part 61 includes the portion fromthe third side 60C to the inner end of the steam discharge part 70. Inthe second example, the anterior peeling part 61 includes the inner endof the steam discharge part 70. If the range of the anterior peelingpart 61 is the range defined in the second example, the inner end of thesteam discharge part 70 is directly communicated with the storage space10C when the anterior peeling part 61 has entirely peeled apart, butbecause the communication area of the steam discharge part 70 isrelatively small, a state where the pressure in the storage space 10C isrelatively high is maintained. Thus, the force acting to peel thesteam-releasing seal part 60 is high, the peeling of the posteriorpeeling part 62 proceeds smoothly following the peeling of the anteriorpeeling part 61.

The steam discharge part 70 can take various configurations. Accordingto the first example, the steam discharge part 70 is a cut or anaperture penetrating the first sheet 21. According to the secondexample, the steam discharge part 70 is a cut or a hole not penetratingthe first sheet 21. The depth of the cut or hole in the second exampleis preferably such a depth that causes the portion of the first sheet 21corresponding to the steam discharge part 70 to rupture when thesteam-releasing seal part 60 peels apart. The steam discharge part 70can take various outer shapes. According to the first example, the outershape of the steam discharge part 70 is a rectangle extending in thefirst direction or the second direction. According to the secondexample, the outer shape of the steam discharge part 70 is a regulartriangle, an isosceles triangle, a square, or a pentagon or a polygonwith more sides. In a state where the peeling of the steam-releasingseal part 60 has not reached the aperture or cut of the steam dischargepart 70, the aperture or cut does not allow the storage space 10C tocommunicate with the outside. In a state where the peeling of thesteam-releasing seal part 60 has reached the aperture or cut, theaperture or cut allows the storage space 10C to communicate with theoutside, and a communication area which is the area of the aperture orcut that communicates between the storage space 10C with the outsideincreases as the peeling progresses.

In the first example or the second example, when the outer shape of thesteam discharge part 70 is formed so as to extend in the direction inwhich the peeling of the steam-releasing seal part 60 proceeds(hereinafter referred to as peeling progress direction), thecommunication area gradually increases in accordance with the progressof the peeling. Thus, the flow rate of the steam discharged outside fromthe storage space 10C does not increase rapidly, and it helps thepeeling of the steam-releasing seal part 60 to reach the apex 60D whichis an edge of the posterior peeling part 62.

The ratio of the dimension HB of the steam discharge part 70 in thepeeling progress direction to the dimension HA of the steam-releasingseal part 60 in the peeling progress direction (hereinafter referred toas discharge part ratio RA) is preferably determined based on therelationship between the ease of steam discharge and the difficulty offoreign substance entering the steam discharge part 70. The formula forobtaining the discharge part ratio RA is “RA=(HB/HA)×100”. The dimensionHA is, for example, the height of the steam-releasing seal part 60 whenthe outer shape of the steam-releasing seal part 60 is a triangle. Thedimension HB is, for example, the long side length of the steamdischarge part 70 when the outer shape of the steam discharge part 70 isa rectangle. A preferable example regarding the maximum value of thedischarge part ratio RA is 62.5%. A further preferable example regardingthe maximum value of the discharge part ratio RA is 25%. When thedischarge part ratio RA is 62.5% or less, foreign substance is lesslikely to enter into the steam discharge part 70. When the dischargepart ratio RA is 25% or less, foreign substance is even less likely toenter into the steam discharge part 70. A preferable example regardingthe minimum value of the discharge part ratio RA is 12.5%. A furtherpreferable example regarding the minimum value of the discharge partratio RA is 25%. When the discharge part ratio RA is 12.5% or greater,the steam is appropriately discharged from the steam discharge part 70when the steam-releasing seal part 60 peels apart. When the dischargepart ratio RA is 25% or greater, the steam is further appropriatelydischarged from the steam discharge part 70 when the steam-releasingseal part 60 peels apart.

FIG. 3 shows the steam-releasing flat pouch 10 of before the opening 40is closed (hereinafter referred to as unclosed steam-releasing flatpouch 10). The contents C (see FIG. 1) is put into the storage space 10Cfrom the opening 40 of the unclosed steam-releasing flat pouch 10. Afterputting the contents C into the accommodation space 10C, heat sealing isapplied to a sealing-planned part 80 where the second seal part 32 isplanned to be formed, and thus the second seal part 32 is formed, andthe closed steam-releasing flat pouch 10 shown in FIG. 1 is obtained.

Referring to FIG. 1, an example of method for using the steam-releasingflat pouch 10 is described.

The closed steam-releasing flat pouch 10 is placed in heating means (notshown) such as a microwave oven such that the second sheet 22 is belowthe first sheet 21, and then it is heated by the heating means. Afterthe heating is finished, the sheets 21 and 22 are torn from the outerend of the notch 52, and a force is applied to the sheets 21 and 22 sothat the tearing of the sheets 21 and 22 proceeds along the perforatedline 51. By separating the separable part 10B from the pouch body 10A,the contents C are extracted from the storage space 10C to the outsideof the steam-releasing flat pouch 10.

Referring to FIGS. 4 to 6, effects of the steam-releasing flat pouch 10is described.

When the closed steam-releasing flat pouch 10 is heated by the heatingmeans, in one example, it is set such that the second sheet 22 ispositioned below and the first sheet 21 having the steam discharge part70 is positioned above. In this state, when the closed steam-releasingflat pouch 10 is heated, the pressure in the storage space 10C isincreased by the steam generated from the contents C, and a force actingto cause the steam-releasing seal part 60 to peel apart is applied tothe steam-releasing seal part 60. Once the pressure in the storage space10C rises to a certain level, peeling of the steam-releasing seal part60 starts from the anterior peeling part 61 and the peeling of thesteam-releasing seal part 60 proceeds toward the posterior peeling part62. As shown in FIG. 4, when the peeling of the steam-releasing sealpart 60 reaches the steam discharge part 70, the steam discharge part 70allows the storage space 10C to communicate with the outside, so thatthe steam in the storage space 10C is discharged to the outside throughthe steam discharge part 70. Thus, the increase of pressure in thestorage space 10C is suppressed, and the force acting to cause thesteam-releasing seal part 60 to peel apart is reduced. However, becausethe seal width XA of the posterior peeling part 62 is smaller than theseal width XA of the anterior peeling part 61, a situation where thepeeling of the steam-releasing seal part 60 stops before the end of theposterior peeling part 62 is unlikely to occur. As shown in FIG. 5, whenthe peeling of the steam-releasing seal part 60 reaches the end of theposterior peeling part 62, as shown in FIG. 6, the portion of the firstsheet 21 that was joined by the steam-releasing seal part 60 movesupward so as to be separated from the second sheet 22 and the contentsC. In the steam-releasing flat pouch 10, the steam-releasing seal part60 is formed in the inner part 23, and the steam discharge part 70 isformed in the steam-releasing seal part 60. Thus, when the first sheet21 moves upward, the steam discharge part 70 also moves upward so as tobe separated from the second sheet 22 and the contents C. Thus, thecontents C are unlikely to leak when the steam is discharged.

(Examples)

The inventor of the present invention performed tests to confirm therelationship between the configuration of the steam-releasing seal part60 and the steam discharge part 70, and the seal peeling performance andthe steam releasing performance, using samples of Examples andComparative Examples. FIG. 7 shows the test conditions of ComparativeExamples and Examples regarding the tests. FIG. 8 shows the testresults. In the following, for convenience of explanation, the samereference numerals are given to the parts of the samples of ComparativeExamples that are common to the samples of Examples. The samples ofExamples are steam-releasing flat pouches 10 according to embodiments.The samples of Comparative Examples are steam-releasing flat pouch 10provided with structures different from the steam-releasing flat pouches10 of the Examples. The steam-releasing flat pouch 10 of eachComparative Example differs from the steam-releasing flat pouch 10 ofeach Example in that the seal width XA of the posterior peeling part 62in the peeling progress direction is larger than the seal width XA ofthe anterior peeling part 61 in the peeling progress direction. Apartfrom this, they have the same configuration as the steam-releasing flatpouches 10 of the Examples.

The specifications regarding the samples of Examples and ComparativeExamples are as follows. The material of the outermost layers for thesheets 21 and 22 is polyethylene terephthalate. Each outermost layer hasa thickness of 12 ?m. The material of the intermediate layer for each ofthe sheets 21 and 22 is nylon. The intermediate layer has a thickness of15 ?m. The material of the innermost layer for each of the sheets 21 and22 is non-oriented polypropylene. The outermost layer has a thickness of60 ?m. The dimension of the steam-releasing flat pouch 10 in the firstdirection is 130 mm. The dimension of the steam-releasing flat pouch 10in the second direction is 135 mm. One steam-releasing seal part 60 isprovided in the inner part 23. The steam-releasing seal part 60 isprovided in the separable part 10B at a position facing the center inthe longitudinal direction of the first seal part 31.

The steam-releasing seal part 60 has an outer shape of a circle in thesamples of Comparative Examples 1 and 5. The circle has a radius of 5mm. The steam-releasing seal part 60 has an outer shape of square in thesamples of Comparative Examples 2 and 6. Each side of the square has alength of 10 mm. The outer shape of the steam-releasing seal part 60 ofthe samples of Comparative Examples 3 and 7 is a trapezoid configuredsuch that the seal width XA becomes wider from the center of the innerpart 23 toward the first seal part 31, that is, in the peeling progressdirection. The length of the upper base of the trapezoid is 10 mm, thelength of the lower base is 20 mm, and the height is 10 mm. The outershape of the steam-releasing seal part 60 of the samples of ComparativeExamples 4 and 8 is a regular triangle configured such that the sealwidth XA becomes wider from the center of the inner part 23 toward thefirst seal part 31, that is, in the peeling progress direction. Eachside of the regular triangle has a length of 10 mm.

The outer shape of the steam-releasing seal part 60 of the samples ofExamples 1 and 3 is a triangle configured such that the seal width XAbecomes narrower from the center of the inner part 23 toward the firstseal part 31, that is, in the peeling progress direction. Each side ofthe regular triangle has a length of 10 mm. The outer shape of thesteam-releasing seal part 60 of the samples of Examples 2 and 4 is atrapezoid configured such that the seal width XA becomes narrower fromthe center of the inner part 23 toward the first seal part 31, that is,in the peeling progress direction. The upper base of the trapezoid has alength of 10 mm, lower base thereof has a length of 20 mm, and thetrapezoid has a height of 10 mm.

The first direction of the steam discharge part has a dimension of 1 mmin the samples of Comparative Examples 1 to 4 and the samples ofExamples 1 and 2. The second direction of the steam discharge part has adimension of 3 mm in the samples of Comparative Examples 1 to 4 and thesamples of Examples 1 and 2. The first direction of the steam dischargepart has a dimension of 3 mm in the samples of Comparative Examples 5 to8 and the samples of Examples 3 and 4. The second direction of the steamdischarge part has a dimension of 1 mm in the samples of ComparativeExamples 5 to 8 and the samples of Examples 3 and 4.

In order to evaluate the seal peeling performance, the inventor visuallyconfirmed whether the entire steam-releasing seal part 60 had peeledapart after heating the closed steam-releasing flat pouch 10 using theheating means. The state where the entire steam-releasing seal part 60has peeled apart is a state where the portions of the first and secondsheets 21 and 22 constituting the inner part 23 are not joined. If theentire steam-releasing seal part 60 peels apart, the seal peelingperformance is evaluated to be good, and if at least a part of thesteam-releasing seal part 60 does not peel apart, the seal peelingperformance is evaluated to be not good.

In order to evaluate the steam-releasing performance, the inventorvisually confirmed whether the contents C had leaked from the steamdischarge part 70 when the closed steam-releasing flat pouch 10 washeated by the heating means to discharge steam from the steam dischargepart 70. The state where the contents C do not leak from the steamdischarge part 70 is a state where the contents C are not attached tothe surface of the first sheet 21 and around the steam-releasing flatpouch 10. The state where the contents C has leaked from the steamdischarge part 70 is a state where the contents C are attached to thesurface of the first sheet 21 and/or around the steam-releasing flatpouch 10. The test was performed three times. The contents C areingredients of beef bowl. The ingredients of beef bowl include beef,vegetables, and soup stock. The contents C has a weight of 80 g. Themicrowave oven has power of 600 W. The heating time of the microwaveoven is 1 minute and 20 seconds.

In the section of the seal peeling performance in FIG. 8, the circlesindicate a case where the entire steam-releasing seal part 60 peeledapart, and the X indicates a case where at least a part of thesteam-releasing seal part 60 did not peel apart. In the section of thesteam releasing performance in FIG. 8, the circles indicate a case wherethe contents C did not leak when the steam was discharged from the steamdischarge part 70, and the X indicates a case where the contents Cleaked when the steam was discharged from the steam discharge part 70.

According to the steam-releasing flat pouches 10 in Examples, it wasconfirmed that, when the closed steam-releasing flat pouch 10 is heatedby the heating means, the entire steam-releasing seal part 60 peelsapart and the contents C are unlikely to leak. In addition, it wasconfirmed that, when the steam discharge part 70 has a shape extendingin the peeling progress direction, the entire steam-releasing seal part60 peels apart and the contents C are further unlikely to leak.

(Modifications)

The description of the embodiments described above is only an exemplaryform of the steam-releasing flat pouch according to the presentinvention, and it is not intended that forms thereof are limited. Thesteam-releasing flat pouch according to the present invention couldencompass, for example, modifications of the above embodiments andcombinations of at least two modifications that are mutually compatible.

The structure of the steam-releasing seal part 60 can be arbitrarilychanged. FIG. 9 shows an example of a modification for thesteam-releasing seal part 60. The steam-releasing seal part 60 includesan anterior peeling part 61 and a posterior peeling part 62. Forexample, the outer shape of the anterior peeling part 61 may be asemicircle. The outer shape of the posterior peeling part 62 is anisosceles triangle whose seal width XA decreases in the peeling progressdirection. The steam discharge part 70 can be provided at any suitableposition inside the outer shape of the steam-releasing seal part 60.According to a first example, the steam discharge part 70 is provided soas to straddle the anterior peeling part 61 and the posterior peelingpart 62. According to a second example, the steam discharge part 70 isprovided only in the posterior peeling part 62 of the steam-releasingseal part 60.

FIG. 10 shows an example of another modification of the steam-releasingseal part 60. The steam-releasing seal part 60 includes an unsealed part71 provided so as to surround the steam discharge part 70. The unsealedpart 71 is a part inside the outer shape of the steam-releasing sealpart 60 where the first sheet 21 and the second sheet 22 are not joined.After forming the steam discharge part 70 in the first sheet 21, if thesteam-releasing seal part 60 is formed by joining the first sheet 21 andthe second sheet 22 so that the unsealed part 71 is formed, thermalcontraction around the steam discharge part 70 in the first sheet 21 issuppressed. This facilitates the steam discharge part 70 maintaining itsdefined dimensions.

REFERENCE SIGNS LIST

-   -   10 . . . Steam-releasing flat pouch; 10C . . . storage space; 20        . . . Sheet; 23 . . . Inner part; 30 . . . Seal part; 50 . . .        Guide part; 60 . . . Steam-releasing seal part; 61 . . .        Anterior peeling part; 62 . . . Posterior peeling part; 70 . . .        Steam discharge part; C . . . Contents.

What is claimed is:
 1. A steam-releasing flat pouch comprising: a sealpart configured to seal stacked sheets so as to form a storage space forstoring contents; a steam-releasing seal part joining parts of the sheetrespectively located in inner parts of the sheet so that the joinedparts are not continuous with the seal part, each inner part being apart of the corresponding sheet inside the seal part; and a steamdischarge part formed in the steam-releasing seal part and configurednot to allow the storage space to communicate with the outside when thesteam-releasing seal part is not peeled apart, and to allow the storagespace to communicate with the outside when the steam-releasing seal partis peeled apart, wherein: the steam-releasing seal part includes ananterior peeling part including a part that peels apart first in thesteam-releasing seal part as a pressure in the storage space increases,and a posterior peeling part including a part that peels apart last inthe steam-releasing seal part; and a width of the posterior peeling partin a direction different from a direction in which peeling of thesteam-releasing seal part proceeds is smaller than a width of theanterior peeling part in the direction different from the direction inwhich the peeling proceeds.
 2. The steam-releasing flat pouch of claim1, wherein: the posterior peeling part is formed so that the widththereof becomes narrower in the direction in which the peeling proceeds.3. The steam-releasing flat pouch of claim 1, wherein: the steamdischarge part includes a cut or an aperture penetrating one of thestacked sheets, and is formed so as to extend in the direction in whichthe peeling proceeds.
 4. The steam-releasing flat pouch of claim 1,further comprising: a guide part constituting a guide for separating thesheet; and a part of the seal part in order to open the storage spaceclosed by the seal part, wherein: the steam-releasing seal part isprovided in parts of the sheet that are separated by the guide part. 5.The steam-releasing flat pouch of claim 1, wherein: a dimension of thesteam discharge part in the direction in which the peeling proceeds is12.5% or larger of a dimension of the steam-releasing seal part in thedirection in which the peeling proceeds.
 6. The steam-releasing flatpouch of claim 1, wherein: a dimension of the steam discharge part inthe direction in which the peeling proceeds is 62.5% or smaller of adimension of the steam-releasing seal part in the direction in which thepeeling proceeds.
 7. The steam-releasing flat pouch of claim 1, furthercomprising: the contents stored in the storage space.